Do not recursively set permissions for the uploads directory

As pointed out in https://github.com/hedgedoc/container/pull/29#pullrequestreview-818294097, recursively setting permissions
is unwanted behaviour.
Signed-off-by: David Mehren <git@herrmehren.de>

resources/docker-entrypoint.sh

@@ -30,7 +30,7 @@ fi
 if [ "$UID" -eq 0 ] && [ "$CMD_IMAGE_UPLOAD_TYPE" = "filesystem" ]; then
     if [ "$UID" -eq 0 ]; then
         chown -R hedgedoc ./public/uploads
-        chmod -R $UPLOADS_MODE ./public/uploads
+        chmod $UPLOADS_MODE ./public/uploads
     else
         echo "
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